AM401000 Critical Materials: transfer AM.20.90.00 custom fields (inherited fields in AM401000) to Purchase Order lines created via Purchase button

I’m working in Acumatica Manufacturing and I need two custom fields from AM.20.90.00 to be copied into the Purchase Order line that is created from AM401000 (Critical Materials Inquiry) when clicking the Purchase  button.

What I have

• In AM.20.90.00 (Production Material) I added 2 custom fields (examples):

  • UsrStucklisteBreiteProd (width / “Breite in mm”)

  • UsrStucklisteLangeProd (length / “Länge in mm”)

• These fields are already filled during production order creation:

  • I override ProdMaint.CopyBomToProductionDetails() and copy values from AMBomMatlExt → AMProdMatlExt.

• In AM401000, the inquiry dataset uses SelectedProdMatl.

  • I created PXCacheExtension<SelectedProdMatl> so the fields appear there.

  • I override CriticalMaterialsInq.BuildSelectedProdMatl() to populate the fields into SelectedProdMatlUsrExtension.

  • Result: the values show correctly in AM401000 (so the fields are “inherited”/available in the inquiry results).

The problem

When I click the Purchase button in AM401000, Acumatica creates the Purchase Order, but the PO line custom fields are empty.

My goal is:
✅ The created PO line (Custom fields) should receive the same values:

• UsrStucklisteBreiteProd

• UsrStucklisteLangeProd

Which logic/extension point should I target to populate the created fields when the PO is created from AM401000 via the Purchase button?